8. Read the passage below about MRI devices, then answer the following questions. Water, composed of hydrogen and oxygen atoms, is a part of all cells. The human body is approximately two-thirds water by mass and contains billions of hydrogen atoms. In a magnetic resonance imaging (MRI) device, magnetic fields interact with these hydrogen atoms, producing images that doctors can use to diagnose injuries and disease. The MRI uses a superconducting magnet to create a large, stable magnetic field of approximately 2.0 T. The large magnetic field is needed to produce precise images of the soft tissues inside the human body. For an MRI machine to obtain images, a patient must lie on a movable bed that slides into a tube in the centre of the magnetic field. Hydrogen atoms in the body can behave like atomic-sized compasses whose north and south poles normally point in random, changing directions. When the body enters the magnetic field, the body's hydrogen atoms align their poles either in the direction of the field or opposite to the direction of the field. The number of atoms aligned with the field will almost equal the number aligned opposite, but there will be a small difference in the numbers (about one in a million). This difference in the number of atoms aligned versus anti-aligned depends on the particular material that the atoms are part of (such as skin, bone, or organs) and whether the material is normal and healthy or abnormal and diseased. Physicians are able to tell the difference between various types of tissues based on these magnetic properties. a) What is the purpose of MRI devices? [1] b) Explain how this device relates to magnetic fields. [2] c) Describe one positive or negative impact this technology has on society, technology, or the environment. [2]